Metallurgical process



I PatentedhMar. 26,. 1946 METALLURGICAL PROCESS Charles H. Heist,Buffalo, N. Y., assignor to National Steel Corporation, a corporation ofDelaware No Drawing. Application March so, 1943,. I

Serial No. 481,147 1 4 Claims.

This invention relates to an improved process for making ferrosilicon.

In the present practice of making ferrosilicon or silvery iron a highlysilicious ore is used together with a high hearth temperature. Aboutone-third of the ore charge is normally Richmond ore or some otherhighly silicious ore. In the case of Richmond ore the silica runs about.40%. The coke burden is kept heavy in order to maintain a hightemperature at the smelting zone. As the charge descends in the furnacethe silica which is present mostly in the form of silicates melts andpart immediately combines with limey substances to form slag. Of thatportion which continues downwardly through the furnace the majority goesto the slagto satisfy the lime before reaching the smelting zone. Ofthat which does reach the smelting zone a portion.

depending among other things upon the hearth temperature, is reduced tosilicon which enters the iron. Silica is reduced in the presence of cokeat a temperature of about 3200 and 3300 F.

Ferrosilicon usually runs from 7 to 15% silicon. An optimum proportionof silicon is 10% due to economic factors of blast furnace operation. Inorder to get 10% silicon into the iron under present. operatingconditions, a quantity of silica equal to about 22% of the ore chargemust be available. When using a highly 'silicious ore the silicon, beingpresent in the form of silicates, is melted at relatively lowtemperatures and is thus available for slagging and side reactions overa'considerable part of the descent in the furnace. Additionally, a largebody of these melted silicates are held in the burden by the blast and,when the blast is reduced for tapping purposes this large body of liquidsilicates rushes down through the smelting zone to -join the slagwithout suiiicient time for reduction. in the smelting zone of some ofthe silica to silicon. This results in loss of silica to-the slagbesides the objectionable factors of a too highly silicious' slag.

In view of thefact that silicon is reduced at the proper temperaturewhen it is in intimate contact with the incandescent coke, theapplitains its form'right down to the point of combustion. Thus in thepresent process the silica is held within the interstices of the cokeuntil i the coke body reaches the smelting zone temperature and isconsumed by combustion. At this point by maintaining the temperaturebetween 3200 and'330'0 F. the silica intimately held in contact with thecoke is reduced to silicon and enters the iron. In the present processsufficient silica for fluxing is supplied by the ores used. If there isnot suflicient silica present in theores, sand may be added to theburden for fiuxing purposes, the silica in the coke being destinedforthe iron. If the economics of the process demands that some highlysilicious ores beused in the charge, less silica can be added to thecoke or more lime used in the charge, the

proportion of silica in the coke being maintained I the proportion ofcoke charged is increased. The

applicant has found that 10% silicon in the iron is still the mosteconomical proportion under present operating conditions. To increasethe silicon appreciably over this necessitates the use of an amount ofcoke which makes the process uneconomic.

In producing his new metallurgical charging stock the applicantdetermines the amount of silica in the coke ash and addssufflcient finesand to the coal charged to the coking process TABLE 1 Stock analysis inper cent Stock Fe Phos SiOa Mn A1203 OeO MgO 55% Hill Bessemer 55.33 0.034 7.77 0. 12 0.37 Rii'hmrmd 35. 32 045 42. 55 i 08 1. 6% (Crude)Portsmouth 39. 95 177 9. 99 2. 76 3% Amsden 51. 53 613 4. 61 2. 96 200#Ro1lscale.. 73. 30 036 70 21 600# Borings 85.00 050 5. 00 20MFerrosilicon scrap 64.45 500 20. 42 Donner m 020 4. 80 HM Stone .011 .92

Hill Bessemer 49. 89 27. 017 3. 87 Richmond 31. 11. 20 014 13. 49(Crude) P 5. 66 2. 26. 010 57 Amsden 3. 40 1. .021 16 Roll scale- 1.89 1. 39 001 01 Borin 5.66 4.81. .003 28 Ferrosilieon scrap 1. 89 1. 22009 39 Average ore 100.00 50. 18 075 18.77 41 1 00 17 18 Weight ofcharge, pounds 6.30 ore 10, 600 5, 319 8. 0 1, 990 43 106 18 19 3.55 mlm7, 097 1. 4 220. 25 11 1.15 500119 2,300 .3 20 1, 097 122 Ore per netton pig iron 3,476 lbs. equals 1.74 tons net.

Total charge, lbs. 810: for 10.00% Si in pig 1,074 I Slag composition111 lbs. per charge theoretical S10: 1, 278 42. 51 39. 50 A 346 11. 5154. 02 12. 20 51. 70 Slag volume 49. 257 C30 1, 37. 92 38. 75 Poundsstone per ton mg 754 MgO 152 5. 06 42. 98 6. 89 45. 64 Pounds slag perton pig.-- 9861! Add. 3% 91 3. 00- 2. 66 Pig iron tons per charge 3.05 ITotal slag 3, 007 100. 00 100.00 I I I Yield 5o.1s+s7.11%-57.e1 I Pig manalysis reg 1g) B101 to bases equals .99

Per cent re... 87.11

Stone required 2,266 lbs.

Table 2 is a furnace-mixture for use under present operating conditionswhich incorporates TABLE 2 Stock analysis in per cent Stoek- Fe PhosSiOa Mn AlzOa CBO MgO 55 Hill Bessemer" 56. 46 0. 033 8. 93 0. l2 0. 375 Amsrlan 53. 21 512 4. 77 16 2. 16 1. 11 0. 54 Slnfer 56. 93 106 12. 7558 2. 20 2. 57 1.50 26 Hanna 49. 06 074 7. 13 I 64 1. 43

.020 15.00 2.94 .40 .14 EM stone" 011 74 79 49. 28 4. 51

Mia-lure ercent Average cre 100.00 55. 80 .079 8 l9 58 94 24 13 Stock FePhos s10. Mn 1110. 0110 M30 Weight of charge, pounds I 018 9, 400 5, 2467. 4 55 88 23 12 Cnlm 7, 157 1. 4 1, 074 210 29 flfnnn 1, 300 1 11. 10M1 59 Ore per ton pig iron 3,123 lbs. equals 1.56 tons net.

Total charge, lbs. 8101101- 10.00% Si in pig 1,194 Slag composition inlbs. per charge Total slag.-...' -.1, 797 100.00 v 1 Yield55.80:-87.07%=64.10% Pig i 'on analysis req ugr ed S10; to bases equals.85

"""" "I 10.00 .03 75 Stone required 1,2901? Percent Fe..- 87. 07 I vTable 3 shows a. furnace mixture in which some cally to incorporate upto 15% of silicon into the Richmond ore is used. The coke used containsiron and even higher percentages may be feasible 15% S102 including thatin the ash.- with improvedconditions or operation.

' TABLE 3 Stock analysis in per cent Stock Fe Phos s10, Mn 41,0. 050 MgO70% Hill Bessemer 50.40 0.033 8.93" 0.12 0.37

5 Amsdem. 53.21 .512 4.77 .10 2.10 1 11 0.54 7 50.03 .100 12 75 .58 2202 57 1.50 7 (Crude Portsmouth 39.95 .177 9.97 4.61 2.70 21 .25 1031011111011 38.29 .053 37. 34 .13 1.40 34 .44 200;; Roll scale.-. 73.30.030 .70 .51 .21 600i Borings 85.00 .050 5.00 .70 Silica-coke .020 15.00 2. 04 1 14 KM stone .011 .34 .70 40.23 4 51 Mixture, percent HillBessemer. I 64. 04 36. 16 021 5. 72 4.58 244 .023 .22 .07 .10 .05 .020.110v 3.01 .007 .57 .15 .1s .10 0. s0 2. 74 .4012 e0 .32 19 01 .02 0.153.50 .005 3.43 .01 13 03 .04 2.13 1. .001 .01 .01 Borings 6. 38 5. 42003 32 04 Average ore 100.00 73 .072 11 20 57 .27 .28

Wei M char 2 ounde 8,600end8000re of 0.0 1,001 '25 20 00k 1.4 210 20 10Stone 2 13 838 77 Ore per ton pig iron 3,124 lbs. equals 1.56 tons net.

Total charge lbs. $10,101 10.007 s1 in pig, 1.103. Slag composition inlbs. per chm-Ere 966' 41. 20 200 12.77 54.03 Slag volume 38. 91% 892 38.11 Pounds stone per ton pig. 565# 113 4. 86 42. 97 Pounds slag per tonpig 7? 71 3.00 Pig iron tons per charge" 3. 01 1 501121112 2,341 100.00

. Yield 5s.7s+s7.07%=04.02 Pig gun analysis rezgltied 310, to basesequals .06.

.1 12 I Stone required 1,0001

Percent Fe... 87.07

It will be understood that the metallurgical I claim: charging stock ofthe present invention can be 1. In a process for producing ferrosiliconin a used in any process of incorporating silicon in a combustion typemetallurgical furnace where metal during reduction. iron ore is reducedand melted bythe heat of in n ygen enriched blast the process ofcombustion, charging iron ore containing silicon the present inventioncan be utilized economi- 75 in combined form to the furnace,chargin'gafluxing agent to the furnace in suflicient quantity toremovethe major portion of saidsilicon in slag form and charging silica andmetallurgical coke to the furnace, the .coke having the silicamechanically held in. its structure in a quantity cient quantity toremove the major portion of suflicient to supply the major portion ofthe silicon in the ferrosilicon product.

2. A process for producing ferrosilicon includins from about 7% to about15% silicon in a comheld in its structure in ajquantity sufflcient tobodies consisting of about 15% silica and the remainder coke andincidental impuritie 'to the furnace, the coke having the fine silicamechanically held in its structure in a quantity sumcient .to supply themajor portion of the silicon in the product; and burning said coke andcausing said fluxing agent to remove the major portionof. said combinedsilicon in slag form from said ore and causing the molten iron tocombine with the silicon of said silica of said bodies in a quantitysufficient to produce said ferrosilicon product.

3. In a process for producing ferrosilicon in-' cluding from 7% to 15%silicon in a combustion. type furnace wherein iron ore is melted by the80 heat of combustion, charging iron ore containing silicon in combinedform to the furnace, charging a fluxing agent to the furnace insufiisaid combined silicon in slag form and charging bodies consistingof about 15% silica and the remainder coke and incidental impurities tothe furnace, the coke having fine silica mechanically supply the majorportion of the silicon in the ferrosilicon product. t

4. A process for producing ferrosilicon in a combustion type furnacewherein iron ore is melted primarily by the heat generated by thecombustion of coke, said process comprising charging iron ore containingsilicon in combined form to the furnace, charging a fiuxing agent to thefurnace in suificient quantity to remove the major portion of saidcombinedsilicon in slag form and charging bodies consisting of silicaand coke to the furnace, the coke having fine silica, mechanically heldin its structure in a quantity sufiicient to supply the major portion ofthe silicon in the product; and burning said coke and causing saidfluxing agent to remove the major portion of said combined silicon inslag form from said ore and causing the molten iron to combine with thesilicon of said bodies in a quantity sufliv cient to produce saidferrosilicon product.

' CHARLES H. HEIST.

